Self assembled and electrochemically deposed layers of thiols on gold compared with electrochemical impedance spectroscopy and atomic force microscopy

Self-Assembling is based on a spontaneous process in which organic molecules (alkanethiols, silanes) are adsorbed on a substrate (gold, glass, silicon). Although the implementation is extremely easy, it shows a big disadvantage in timing, because the solution has to be in contact overnight with the substrate under mild shaking. An alternative method of molecular deposition is the Electrochemically Deposed Multilayers commonly used in our laboratory for further immobilization of biological molecules in order to obtain specific biosensors for several analytes. It consists in applying a constant potential on gold working electrode (1.3 V vs. Ag/AgCl) for driving molecules in proximity of the electrode and allow them to react on the surface and form a layer similar to self assembled ones. Both the layers, self assembled and electrochemically deposed ones, were tested with Electrochemical Impedance Spectroscopy and Atomic Force Microscopy. The substrate electrochemically covered shows a higher and a more homogeneous deposition than self assembled one and the deposition time is extremely reduced from several hours to a few of seconds (50 s).